Iranian television on Tuesday claimed that a Washington-based Lebanese citizen missing in Teheran since September is actually a US spy now in the custody of authorities.

However, those who know Nizar Zakka - who holds permanent-resident status in the United States - said an image of him in army-style fatigues shown on Iranian state TV came from him recently taking part in a homecoming parade as an alumnus of his military high school in Georgia.

Through a lawyer, the Zakka family said they were "shocked by these false accusations", and stressed that he has no "relation with any military, security institution or secret services whatsoever".